The present disclosure generally relates to implantable medical devices, and more particularly to tissue expanders, which may be used in drug delivery.
A typical tissue expander includes an inflatable balloon, an injection port, and a hollow lumen that places the injection port in fluid communication with an interior of the inflatable balloon. In use, the balloon is implanted below the surface of the skin in a deflated configuration. A saline solution is then injected through the injection port to expand the balloon to an inflated configuration. The inflated balloon stretches the overlying skin, causing the skin to grow. To facilitate the slow and continued growth of healthy skin, the tissue expander is normally filled in an iterative process that includes partially inflating the balloon in an initial expansion session and further inflating the balloon in subsequent expansion sessions.
Tissue expanders are most commonly used in breast reconstruction surgery following mastectomy to form a skin pocket for holding a permanent breast implant. After the tissue expander is removed, the newly grown skin is left in place and a permanent breast implant is inserted into the empty pocket. Tissue expanders also are used to grow skin that is transplanted to other locations on the body to replace or supplement skin that has been damaged due to burn, trauma, accident, surgery, or birth defect. Increasingly, tissue expanders are used for scalp restoration, where healthy scalp tissue is grown that supports hair follicles.
One problem with tissue expansion is that the implantation site may be painful in the hours or days after the tissue expander is initially inflated. For example, many patients report feeling pain for about the first 24 to 72 hours after the expander is inflated. This pain is normally treated with pain relievers that are delivered systemically, such as a narcotic analgesic. Local drug delivery to the implantation site could be achieved directly from the tissue expander itself, although previous attempts to achieve such local delivery have proved ineffective.
Prior researchers have attempted to deliver drug directly from the inflatable balloon. The balloon was loaded with a lidocaine and saline solution with the intent of diffusing the lidocaine directly through the surface of the balloon into the surrounding environment. In vitro testing demonstrated that lidocaine did diffuse through the balloon surface. However, in vivo testing showed that the actual diffusion rate was minimal and to achieve a therapeutic delivery rate, the balloon would need to be loaded with an amount of lidocaine that would prove toxic in the event of implant rupture.
A double-chamber tissue expander also has been proposed for the purpose of achieving drug delivery. The double-chambered tissue expander includes an inner non-porous bladder, an outer porous bladder, and ports in communication with each of the bladders. In use, the outer bladder may be loaded with a lidocaine solution, while the inner bladder is loaded with an inflating solution. The expansion of the inner bladder with the inflating solution instantaneously drives the lidocaine solution from the outer bladder into the implantation site. Because the drug is delivered relatively instantaneously, however, a patient may not be adequately treated for pain experienced hours or days following inflation of the tissue expander or following subsequent inflations of the tissue expander.
It is therefore apparent that a need exists for improved systems, devices, and methods for delivering drug directly from a tissue expander. Such systems, devices, and methods desirably would provide local drug delivery from the tissue expander over an extended period.